Can I insert a tab in the replace text ? eg. -or '$1\t$2'

[Binger-cn]

Now using '$1\t$2' results in : [group1]\t[group2] , not [group1] [group2]

[BurntSushi]

You can, but you have to insert it literally. The replacement directive doesn't support escape sequences. Inserting it literally depends on your terminal/shell environment. In my environment, if I hit CTRL-v, release it, and then press TAB, it will insert a literal tab character.

[condekind]

An option that allows you to use \t: add $ before your replace string, which must use single quotes, e.g., --replace=$'$1\t$2'
Full example:

$ cat example.txt
foo="this is foo"    hello _bar="this is bar" bye
    hmm hi foo="more foo" but   bar="more bar" ok...

$ rg -P '^.*foo="(.*)".*bar="(.*)".*$' --replace=$'\n${1}\t${2}\n\n'
./example.txt:
this is foo	this is bar

./example.txt:
more foo	more bar

As shown above, you can also use \n and other similar escapes (\0 is also quite useful)